M.Ecos - Ecology Ecos = “home” Ecos Ecology: the study...

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Unformatted text preview: Ecology Ecos = “home” Ecos Ecology: the study of • …where an organism lives. – Range – Habitat – Distribution • …how/why it lives there. – Environment: factors of the habitat that affect the organism – Niche: role of the organism affecting the environment Ecology THE REALM OF ECOLOGY •Biosphere Biosphere Ecosystems •Ecosystem •Community THE REALM OF ECOLOGY • Biosphere • Ecosystem • Community Ecology: Interactions among members of all of the species in a given habitat. Communities Populations • Community • Population Ecology: Ecosystems Communities Interactions among members of the same species in a given habitat. Organisms Populations Organisms Biosphere Ecosystems Communities THE REALM OF ECOLOGY • Biosphere • Ecosystem Ecology: Interactions between the species in a given habitat and their physical environment. Biosphere Ecosystems Communities Populations Organisms Heyer • Biosphere Biosphere • Ecosystem •Population •Organismal Ecology: How an individual organism adjusts its physiology and/or behavior to respond to its environment. THE REALM OF ECOLOGY Populations Organisms 1 Ecology THE REALM OF ECOLOGY • Biosphere Ecology: Interactions among all the ecosystems on the planet — Earth as a living system. Biosphere SPECIES and POPULATION • Species Ecosystems – Interbreed – Fertile offspring • Population Communities – Interacting group of same species – Share resources – Geographical range Populations Organisms Exponential Growth Population growth patterns: changes over time • Population size (N) depends on: – – – – – Natality = birth rate (b) Mortality = death rate (d) Immigration = migration into the population (i) Emigration = migration out of the population (e) Growth rate (r) = (b-d) + (i-e) • Population multiplies by a constant factor. • Growth rate not limited by resources. • “J”-shaped growth curve. Outcome of Exponential Growth • r : population potential growth rate • K : carrying capacity – The maximum population that the environment can sustain over long periods of time. – Determined by biotic and abiotic limiting factors. Heyer • Exceed carrying capacity (K) & crash. – cyclic exponential (“J-shaped) growth curves punctuated by crashes. – typical of species who make tons of tiny kids – “r -selected species” K 2 Ecology Fort Bragg, CA “Boom and Bust” Population Cycles LOG SCALE “Boom and Bust” Population Cycles • “r-selected” • “r-selected” • • Population cycles between a rapid increase and then a sharp decline. Logistic growth • Growth is limited by density-dependent resources or other factors • As population nears the carrying capacity (K), birth rate decreases. • Decrease growth rate produces “S”-shaped curve • “K-limited growth” Fur seal population Exponential vs. Logistic Population Growth • “r-selected”: J-type growth rate limited by r, but cannot be sustained indefinitely beyond K. • “K-selected”: S-type growth rate limited by K Heyer Population cycles between a rapid increase and then a sharp decline. Laboratory populations with defined resources exhibit density dependence “K-selected” Carrying Capacity • Population size that can be sustained by a habitat • Requires renewable resources • Carrying capacity (K) changes as resources flux with size of population • If a population does not limit its size to the carrying capacity, it will deplete its resources and suffer a sharp crash in numbers due to starvation and/or disease — “boom & bust” pattern. 3 Ecology Life History Traits Adult size Small Large Reproduction Semelparous Iteroparous Fecundity Very high Low Newborn size Small Large Dispersal of young Parental care High Low/none Low High Precocial Altricial Juvenile mortality Very high Low Survivorship curve Human Population Growth r-selected K-selected Juvenile predation / Competition Sporadic catastrophes Short (young) Long (old) Newborn behavior Life History Traits For species inhabiting unstable, unpredictable environments ; or species with very high juvenile mortality : • The odds of suitable habitat for the next generation are low. • Therefore, natural selection favors the generalist populations that opportunistically harvest any available resource to grow as fast as possible when they can, and quickly produce many offspring distributed over a wide area to increase chance of hitting someplace good. ( “weeds ”) • “r-selected” — select for high reproductive potential q For species inhabiting stable environments : • Long-term strategy is most successful. • Natural selection favors the specialist populations that excel at harnessing the particular available resources to displace competitors. Spend resources on becoming dominant species and increasing the odds of a few offspring to succeed with you. • “K-selected” — select for intrinsic growth limitations for sustainable population over time. q Type: Major source of mortality Generation time (age) Type III Type I Pop. growth curve Trade-offs, game theory and the allocation of resources Cyclic (boom/bust) S-shape Humans can artificially increase carrying capacity • Technological advances avoid natural growth constraints – Hunting and gathering – Agricultural revolution – Industrial revolution – Scientific revolution • Paradox or time bomb??? The history of t uman population growth • Homo sapiens has life history hraits that should correlate with a K-selected,pop now increasescby 88.4 mill./yr. • Human S-shaped growth urve. • But,–our actual ew LA every twois eeks !! That ’s a n growth curve w exponential!!! • What happens to a population that exceeds its carrying capacity? Human carrying capacity is not infinite • Resources will eventually be depleted • Economic resources allow exploitation of natural resources • Industrialized nations consume more resources per capita Earth’s Human Carrying Capacity • • • Ecological Footprint = land per person needed to support resource demands US footprint is 10X the India footprint Countries above the mid-line are in ecological deficit (above carrying capacity) Ecological footprint vs . ecological capacity Heyer 4 Ecology Ecological Footprint Your Personal Footprint! • Countries above the mid-line are in ecological deficit (above carrying capacity) • United States ß 4.7% of the world population ß Produces 21% of all goods and services ß Uses 25% available processed minerals and nonrenewable energy resources ß Generates at least 25% of world ’ s pollution and trash • India ß 17% of the world population ß Produces 1% goods and services ß Uses 3% available processed minerals and nonrenewable energy resources ß Generates 3% world ’ s pollution and trash • U.S. consumes 50 times more resources than India (per person) • US footprint is 10X the India footprint • The overpopulation and overconsumption by the human population are triggering an enormous array of problems, ranging from food sources (agriculture, fisheries), waste, air and water pollution, energy and mineral use, habitat destruction, and species extinction. You can calculate your own ecological footprint by going to the following URL: http://www.mec.ca/Apps/ecoCalc/ecoCalc.jsp? Ecological footprint vs . ecological capacity Biodiversity Community Ecology Community: All the populations of organisms living together in a given place Characteristics: • Biodiversity — • Levels of biological diversity – Species richness – Relative abundance • Dominant vegetation • Stability/disturbance Redwood forest community Biodiversity Hot Spots • A biodiversity hot spot is a relatively small area with an exceptional concentration of endemic species and a large number of endangered and threatened species • Particularly resulting from habitat destruction. • Most impacted biomes: – Tropical rain forest – Chaparral Terrestrial biodiversity hot spots Extinction is forever Hundred-heartbeat club-members • Endangered species ß In immediate danger of becoming extinct throughout its range (a) Philippine eagle (b) Chinese river dolphin • Hundred-heartbeat Club ß <100 individuals left! • Threatened species Equator Figure 55.17 Heyer ß Likely to become endangered in the foreseeable future if current trends continue (c) Javan rhinoceros 5 Ecology The Extinction Vortex • A diminished population is prone to positive-feedback loops t hat draw the population down an extinction vortex • Once population size is reduced to a critical level [the Minimum Viable Population ], it may not be able to recover! THE PROBLEM OF INTRODUCED SPECIES Small population Inbreeding Genetic drift Lower reproduction Higher mortality Loss of genetic variability Reduction in individual fitness and population adaptability • • • • • • • Zebra mussels Introduced from Caspian Sea Ballast water 750,000 per m2 Reduce phytoplankton levels Loss of fish Cover every hard surface • Clogged water intake pipes Smaller population THE PROBLEM OF INTRODUCED SPECIES • African honeybee • Wanted to cross-breed with honey-bee • Escaped • Aggressive towards humans and animals • Ten deaths in U.S. Biogeochemical cycles: Earth’s Ecosystems • Ecosystem Ecology: Interactions between the species in a given habitat and their physical environment. Global Water Cycle "life-earth-chemical" • Materials enter producers from atmosphere or soil. • Return to abiotic world through respiration and decomposition. • Biologically important materials: – Water (H2O) – Carbon (CO2) – Nitrogen (N2, NO3-, NO2-, NH4) Heyer 6 Ecology Desertification Human activity disrupts local water cycles • Irrigation • Clear cutting of forests – Watershed disturbance Africa – Loss of minerals through runoff – Desertification U.S. 1930’s Dust Bowl DESERTIFICATION Carbon cycle • Carbon dioxide gas (CO2 ) in atmosphere • Plants (producers) use solar energy (sunlight) used to convert CO2 into sugars (photosynthesis) 6CO2 + 6H2O + energy fi C6H12O6 Moderate Severe Very Severe Consumers eat carbon compounds made by producers Carbon Cycle • Glucose, proteins, fats, nucleic acids • Used to produce energy (ATP) • Produces CO2 as waste • CO2 exhaled back into atmosphere C6H12O6 fi 6CO2 + 6H2O + ATP Heyer 7 Ecology Pyramid of production Eating high on the food chain is expensive! • Less than 10% biomass is passed on to next trophic level Real and potential human insults to the integrity of the biosphere Combustion: burning dead organisms returns CO2 to atmosphere 1. Global contamination (pollution) 2. Habitat destruction 3. Global warming 4. Nuclear winter Nuclear 5. Destruction of the ozone layer 5. • Wood • Fossil fuels: Organic litter was transformed into coal or oil – Geological pools used much faster than they are replaced excess CO2 in atmosphere Global habitat impact: the Greenhouse effect • “Greenhouse gases” (esp.., CO2) are transparent to sunlight but absorb infrared radiation Æ trap heat within atmosphere Heyer 8 Ecology Increase in atmospheric CO2 correlates with increase in global temperature Increase in CO2 Other Greenhouse Gases Increase in global temperature Probable consequences of the greenhouse effect OCEAN CURRENTS • Melt polar ice caps, raise sea levels – Flood heavily populated coastal areas – Disrupt major ocean currents / Create temperature extremes • Alterations in global precipitation patterns – Desertification of agricultural areas – Deplete snow-pack water reserves • Major changes in habitats leading to population shifts and loss of biodiversity IMPACTS OF GLOBAL WARMING • Change in sea level – Coastlines – Islands • Heat absorbed by ocean waters at the equator is distributed northward. • Greatly moderates climate extremes. • Warm zones especially expanded along western boundary currents. IMPACTS OF GLOBAL WARMING • Geographical shifts – Animals – Plants • Food supply Heyer 9 Ecology The Miraculous Coincidences of Planet Earth OZONE LAYER • Unique essential combination of factors compatible with life. • Water in all three phases • Size: smallerfilose oxygen • UV radiation absorbed by ozone layer • Chemicals produced by humans are destroying the ozone layer • UV radiation causes mutations – Tan today … Cancer tomorrow – Cataracts in eyes – Deterioration of producers • Especially phytoplankton • Must have sun exposure for photosynthesis • No food produced Æ No life Even our position in the galaxy is ideal! You are here If you were here, the high stellar density would create radiation and gravitational disruption. If you were out here, there would be insufficient heavy elements to form planets. Heyer bigger fitrap hydrogen • Distance from sun: 5% closer fitoo hot 1% farther fitoo cold Very likely unique in the universe! • Speed of rotation, tilt of axis, speed & shape of solar orbit fi prevent lethal extremes • Gas giants in outer solar system deflect interstellar debris Biophilia a love of life and its forms Our innate sense of connection to nature may eventually motivate a realignment of our environmental priorities Biologist Carlos Rivera Gonzales examining a tiny tree frog in Peru 10 ...
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